Be jeezus that's awful. I'd hate to think what the rest of the build is like, or even the things you can't see.
Remember that once the builder has been paid and is off site, it's very very difficult to get things rectified. And that roof should be damp and problem free for decades - and it looks like it will only be months.
yes, you are absolutely right. Here I just showed the front roof. We also did side and rear extension where roof has same problems (leading flashing is wrong; batten gauge is wrong). Nightmare to us now.